1. Technical Field
The present invention relates to a screen.
2. Related Art
Screens in the related art are used by projecting image light projected from a projector or the like in an enlarged scale on a screen surface of a flexible sheet type screen body. Among these screens, there are various portable-type screens used by being carried by users.
Among the portable-type screens, a screen used by opening and closing the screen body in the lateral direction generally includes a screen body on which image light is projected, columns for supporting the screen body on the right side and the left side, opening and closing mechanism for opening and closing the screen body in the lateral direction, and a main column for holding the screen body, the columns, and the opening and closing mechanism. These components are generally arranged in such a manner that the screen body and the columns are arranged in the front and the opening and closing mechanism is arranged behind, and the main column is arranged further behind.
In the structure of the general portable-type screen, since the components are arranged as described above, the center of gravity of the screen is shifted toward the front of the main column, and hence the screen is liable to fall toward the front. Therefore, in order to hold the screen vertically upright with respect to a surface of installation, countermeasures such as improving rigidity of the main column, upsizing a supporting leg for supporting the screen upright, and so on are taken.
A screen disclosed in JP-A-2007-219279 is configured in such a manner that a left movable column is supported by a left end of a pantograph mechanism which is expanded and contracted in the lateral direction, and a right movable column is supported on the right side thereof, and a center portion of the pantograph mechanism is held by a fixed column. Then, the screen body is extended between the right movable column and the left movable column. At least one of the right movable column and the left movable column includes a winding and storing unit for the screen body. The screen includes a driving mechanism for providing a driving force to the pantograph mechanism, and the driving mechanism includes a clutch unit. The screen in this configuration is configured in such a manner that the pantograph mechanism is expanded and contracted by driving the driving mechanism, whereby opening and closing of the screen is automatically achieved. When the expansion and contraction is disabled because the pantograph mechanism comes into contact with an obstacle, the clutch unit is activated to protect the driving mechanism.
However, the screen disclosed in JP-A-2007-219279 has problems such that the configuration of the screen body is generally complicated and is upsized, thereby increasing the weight. Therefore, it is not suitable as a portable-type screen used by being carried by users.
In the general portable-type screens described above, increasing of the thickness of the main column is necessary in order to improve the rigidity of the main column because of the configuration of the screen, so that the screen apparatus is upsized and is increased in weight correspondingly. Accordingly, the portability of the screen is lowered, which results in lowering of the convenience of the screen. Therefore, a screen having a structure in which the weight balance is well achieved, a structure in which the downsizing is achieved, and a structure in which the convenience is improved is demanded.
In the case of the general laterally opening screen, since the weight of the side where the screen winding function is provided (for example, the right column) is increased, the screen gets out of weight balance between the left and right when being deployed, so that the screen might be inclined as a whole. In order to prevent this event, a dummy weight is generally added on the opposite side (left side).
However, the dummy weight simply results in weight increase, so that there arises a problem of lowering of the portability.
Therefore, in the invention, a screen deployment assisting spring is provided on the side opposite from the side where the screen winding function is provided so as to also function as the dummy weight. This spring is relatively heavy, and hence functions as the dummy weight.